matus

That seems to be definetively my case, both codes that I am using are 7 characters long.

Thanks for the research @markerx, will ignore the alert and run some tests to see what happens.

Trying to debug the problem, I installed GTM codes manualy on a simple html website.

There, Tag Analyzer also shows me the same error message.

On this static website I am using a new container, on a new GTM account, copy codes from GTM and paste them where GTM sais they should go.

I am starting to wonder if the problem could be somewhere else but the WP plugin

Similar case here.

I have 4 tags: 1 Analytics, 1 Remarketing, 2 AdWords.

Both the Analytics and Remarketing tags are validated by the Tag Assistant.
The 2 AdWords tags are shown as having an invalid account ID.

Re. container code placement, I’ve tried ‘Foother of the page’ and ‘Codeless injection’, both fail with the same message.